New to an 1984 Mustang

I just bought a 2019 Bullitt in st Augustine fl on March 23 2019 sooo happy! I drove to the store to get my son an icee and a guy in a dodge magnum was in lot I pulled in beside him. I run my car on quite exhaust mode because it is a sleeper .When I came out from store he jumped in to his car.when I started my Bullitt it was quite like a vettSo this guy starts reving his engine! I reached over and toggle my exhaust selection to track . That’s when the warning comes up for you to read the manual because it’s illegal on the streetof course I reved my car up and it sound like it was going to bite his cars head off end of car reving . I drove off slowly and left him quietly in the parking lot.